GEOLOGICAL SOCIETY OF THE PHILIPPINES
GEOHAZARDS AND LANDSLIDE MODELLING OF BAGUIO CITY USING THEMATIC MAPS
Marie Iris Villanueva, Raymund Abundo and Claro Jose Manipon
A Geo hazard map of Baguio City was made using several thematic maps that were processed using GIS vector and raster modes. The base maps used was on a scale of 1:10,000 published by NAMRIA (1995) although the 1957 1:50,000 scale map was also consulted. From these maps, the following data were extracted: vegetation, built – up areas, road network and slope angles. The other data used were landslide maps. A terrain classification map was also produced from interpretation of old aerial photographs (c. 1950).
The four major geo hazards identified were flooding, subsidence due to karst development, landslides and earthquake. In addition to historically flooded areas of City camp and Burnham park, the other potential flood-prone areas are the large sinkholes around the city and the banks of Balili River. Empirical modeling of the landslide areas after the July 1990 earthquake revealed the following: (1) the majority of landslides that happened were not on steep slopes; (2) areas underlain by the Baguio formation experienced the most number of landslides; (3) areas vegetated by shrubs have more number of small landslides coincided with road networks; (5) karst topography and wide valley terrain with convex slopes contributed motre landslides than other types of terrain; (6) almost all large landslides occurred within 500 meters of a large fault.
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